The present invention relates to primary cells of the "dry" type, more particularly to the use of aluminum base alloys as the anode material therein, said anode material also serving as the container for the cell. The present invention also relates to the use of aluminum base alloys as anode material in applications which require resistance to corrosion, such as water heaters.
Zinc is extensively employed as anode material in the construction of dry primary cells, for example, in common flashlight batteries. Numerous proposals have been made to substitute aluminum or aluminum alloys for zinc as the anode material in dry cells in order to utilize the numerous advantageous properties of the aluminum or aluminum alloys. Aluminum and aluminum alloys are generally less expensive than zinc. As zinc becomes more and more scarce, this price differential will increase. Aluminum and aluminum alloys also enjoy a greater ease of fabrication to thin gages and particularly to formed dry cell battery cases.
Dry cell batteries containing aluminum, aluminum-zinc alloys or other aluminum base alloys as the anode material have, however, suffered from numerous significant disadvantages. Such cells generally require the placement of a semi-permeable membrane within the battery container to prevent the evolution of large volumes of hydrogen gas resulting from the aluminum-electrolyte reaction which takes place within the dry cell battery. Dry cell battery containers which have been manufactured from standard commercial aluminum alloys such as Aluminum Association Alloy 1100 are subject to unacceptable hydrogen gas evolution when used. Such hydrogen evolution causes the battery containers to either swell or, in extreme circumstances, to burst. Either condition is not acceptable to the ultimate consumer, since a swollen battery usually cannot be removed from a device into which it has originally been inserted and a battery which has burst may subject the consumer to dangerous corrosive chemicals.
As mentioned above, this evolution of hydrogen gas has presented a problem which has attempted to be solved through the use of a semi-permeable membrane within the battery case which retains the electrolyte material away from the aluminum of the anode casing. Such a solution has not been successful with the typical commercial aluminum alloys. Composite alloys which have been utilized to overcome the gas evolution disadvantage have not been entirely satisfactory and are also quite expensive.
It is, therefore, an object of the present invention to provide an improved primary cell of the dry type.
It is a further object of the present invention to provide an improved primary cell of the dry type which utilizes an aluminum base alloy as the anode which also serves as the container for the cell.
It is a further object of the present invention to provide a primary cell of the dry type as above which reduces the incidence of hydrogen gas evolution within the cell.
It is an additional object of the present invention to provide anode material formed from an aluminum base alloy which is resistant to corrosion.
Further objects and advantages of the present invention will appear from a consideration of the following discussion.